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Precambrian Period page 1
(4600-540 million years ago)

The Precambrian Period is the longest period in Earth's history.  It lasted from the formation of the Earth about 4.6 billion years ago right up to about 540 million years ago.  If Earth's history were changed into a dollar, the Precambrian Period would be worth about 88 cents!

Birth Of A Double Planet

In the first 800 million years, known as the Hadean Eon, the Earth and Moon formed to become what many scientists call a double planet.  They are called this because the Earth and Moon are both large enough to be planets (the Moon is larger than Pluto!) and they are close enough in space to  have one orbit the other.  The Earth and Moon formed through the process of smaller bodies of planet building material colliding with larger bodies as described in the Nebula Theory section of the timeline on this site.  

Two Planets?

Earth and MoonThe Earth and Moon formed side by side during the Hadean Eon of the Precambrian Period.  The Hadean Eon gets its name from the greek god of the underworld, Hades.  Why do you think it was named for this particular god?
(Click on the image for a closer look.)
Image Credit: NASA

Recycling The Earth

Mt. St. HelenThe oceans and atmosphere formed from water vapor and other gases bubbling out of the early molten Earth.  The water may have come mostly from comet collisions as the young Earth was forming.

Today, volcanic activity recycles elements that replenish the Earth's crust, atmosphere and oceans.

(Click on the image for a closer look.)
Image Credit: USGS



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